A conventional typical manipulator which manipulates a minute object has an arrangement as shown in FIG. 16 (Japanese Patent Laid-Open No. 6-90770). Reference numeral 100 denotes an inverted microscope having a movable specimen table 101. A manipulation target object such as a cell in a petri dish 102 and the distal ends of manipulators 103 and 104 are observed through the inverted microscope 100. The micromanipulators 103 and 104 made of glass or the like are attached to holders 105 and 106 with triaxial actuators, respectively. Of the two manipulators 103 and 104, the manipulator 103 is used to hold the target object. The manipulator 104 controls the attitude of the target object or executes operations such as enucleation or nucleus transplantation for it.
FIG. 17 is an enlarged view showing such cell manipulation. FIG. 17 shows a state in which the operation manipulator 104 is perforating a cell 107 having a cell nucleus 108 to enucleate the cell 107. The manipulators 103 and 104 are hollow glass capillaries. The distal end of the manipulator 103 is rounded to be suitable for grasp and not to damage the target object. The manipulator 104 has an appropriately sharpened distal end so that fine manipulation can be performed. For example, to enucleate the cell, the attitude of the cell 107 is controlled by rubbing and rotating it with the operation manipulator 104, as shown in FIG. 18A. Since the cell nucleus 108 is normally present at a one-sided position, the cell nucleus 108 is placed at the opposite position of the holding manipulator 103 (FIG. 18B). At this time, the suction force of the holding manipulator 103 is appropriately adjusted in synchronism with the movement of the operation manipulator 104. To release the cell 107, the pressure in the capillary of the holding manipulator 103 is changed to a positive pressure.
FIG. 19 shows another conventional manipulator (Japanese Patent Laid-Open No. 9-201783). Reference numeral 110 denotes a contact portion to a manipulation target object; and 109, a heater. Projecting and recessed portions 111 and 112 are formed in the contact surface to the target object to reduce the interaction force in grasping it. More specifically, the interaction force such as Van der Waals force or surface tension is reduced by decreasing the contact area to the target object. The heater 109 is arranged near the contact portion 110. The target object can be chucked/released by causing the heater 109 to generate heat to set, in the recessed portion 112, a pressure different from the peripheral pressure.
In the manipulators shown in FIGS. 16, 17, 18A and 18B, however, since the main body is made of glass, the flexibility is poor, and the degree of freedom at the working end is limited. For this reason, the workability in fine work is considerably poor. Such work is normally done under a microscope, and the visual field for it becomes narrow in inverse proportion to the magnification, resulting in difficulty in work. For example, when the attitude of the cell 107 is to be controlled, as shown in FIGS. 18A and 18B, the manipulator 104 can perform only a simple operation such as rubbing under remote control. For accurate and quick work, skills based on advanced training are necessary. In addition, the suction force of the holding manipulator 103 must appropriately be controlled in synchronism with rotation. During this work, the cell 107 often accidentally moves off its position. Furthermore, in a minute target object, the area force such as Van der Waals force or surface tension becomes large relative to the volume force such as gravity or inertial force. In this case, it may be impossible to release the target object that sticks to the manipulator.
The example shown in FIG. 19 takes a measure against this problem. However, the change in pressure is insufficient as a force. For a fine operation such as attitude control, the manipulator itself must largely move. Hence, the work is difficult in a narrow visual field. For the same reason, attitude control cannot be performed while keeping the target object firmly grasped. The influence of direct contact between the contact portion 110 and the target object is also sometimes nonnegligible.